1. Field of the Invention
The present invention relates to a vehicle surroundings monitoring apparatus for a vehicle, capable of detecting moving objects, such as vehicles traveling around a vehicle provided with the vehicle surroundings monitoring apparatus (hereinafter, referred to as xe2x80x9chost vehiclexe2x80x9d) on the basis of images provided by a fish-eye lens.
2. Description of the Related Art
Various types of vehicle surroundings monitoring apparatuses have been proposed and applied to practical uses in recent years for the improvement of safety of vehicles. Those vehicle surroundings monitoring apparatuses are capable of three-dimensionally recognizing roads and traffic conditions in a practically satisfactory accuracy and in a practically permissible time by obtaining images of scenery extending ahead of the host vehicle or objects lying in front of the host vehicle by a cameral and processing the images.
A technique proposed in, for example, JP-A No. 283461/1998 by the applicant of the present patent application subjects images taken by a pair of cameras (stereo camera) to a stereoscopic process to detect the preceding vehicle and obstacles.
It is desirable, for the further improvement of the safety of the host vehicle, to give information about other vehicles and the like traveling beside the host vehicle to the driver in addition to that about a space in front of the host vehicle. Preferably, an image of scenery extending around the side of the host vehicle is obtained by a camera provided with a fish-eye lens to acquire information about a wide range of the side scenery. For example, a technique disclosed in JP-A No. 202180/1997 obtains an image of the side scenery by a fish-eye lens camera, converts the image into a regular image signal by a coordinate transformation circuit, and displays an optional region of a rectified image on the screen of a monitor. However, since this technique merely displays the image of a predetermined part of the vehicle""s surroundings on the screen of the monitor, it is difficult to give the driver distance information representing distances between the host vehicle and other vehicles traveling beside the host vehicle.
To deal with such a difficulty in giving the driver distance information, a technique disclosed in, for example, JP-B No. 2611173 uses a monitoring system including a plurality of cameras respectively provided with fish-eye lenses. The monitoring system calculates three-dimensional coordinates indicating the three-dimensional position of a moving object on the basis of a plurality of wide-angle images provided by the plurality of cameras to acquire distance information about the distance between the host vehicle and a vehicle traveling beside the host vehicle. However, it is not economically preferable to use such a monitoring system of complicated construction for obtaining information about a side space extending around the side of the host vehicle, which may be rough as compared with information about a forward space extending in front of the host vehicle.
The present invention has been made in view of such circumstances, and it is therefore an object of the present invention to provide a vehicle surroundings monitoring apparatus of simple construction capable of obtaining proper information about the surroundings of a host vehicle.
According to one aspect of the present invention, a vehicle surroundings monitoring apparatus for monitoring the surroundings of a host vehicle includes: image obtaining means each having an imaging lens system including a fish-eye lens; an image processing means capable of detecting a moving object on the basis of an optical flow between two images obtained by the image obtaining means respectively at different times, by using one of the images as a reference image, and of setting a representative point representing the moving object on the surface of a road; and an calculating means for calculating the position of the moving object relative to the vehicle on the basis of a displacement angle of the representative point from the optical axis on an image.
In the vehicle surroundings monitoring apparatus according to the present invention, the image obtaining means are disposed on right and left side parts of a body included in the host vehicle.
In the vehicle surroundings monitoring apparatus according to the present invention, the imaging lens system has an optical axis inclined slightly rearward to a direction parallel to the width of the vehicle.
In the vehicle surroundings monitoring apparatus according to the present invention may further include a display means for displaying the positions of moving objects relative to the host vehicle, capable of indicating the velocities of the moving objects relative to the host vehicle by vector notation.